Automatic safety control for arc welding



Dec. 5, 1944.

R. S. KEN RICK AUTOMATIC SAFETY CONTROL FOR ARC WELDING Filed sept. '7, 1942 2 Sheets-Sheet 1 RALPH s. KENR/l/:K

-v His ATTDHNEY e? Dec. 5, 1944. R. s. KENRlcK AUTOMATIC SAFETY CONTROL FOR ARC WELDING 'Filed sept. 7, 1942 2 Sheets-Sheet' 2 Mmm M lNvENTuR.- RALPH 5'; HEAR/'DK His ATTCRQEY former obtains Patented Dec. 5, 1944 AUTOMATIC SAFETY CGNTROL FOR ARC i 1 WELDING Ralph S. Kenrlck, Chicago, lll., assignor to Pullman-Standard Car Manufacturingl Company,

Chicago, Ill., ay corporation of Delaware Application September 7, 1942, Serial No. 457,551

1-0 Claims.

This inventionfrelates to electric arc welding circuits with means designed to isolate the high open-circuit voltage of the welding transformer from the electrode holder when the operator breaks the arc and stops welding.

An important object of the invention is to provide means automatically to effect the opening of the primary circuit of the welding transformer to prevent; power drain thereby from the source of power.

Another and important object of the invention is to provide means automatically to effect the opening of one or the other of the transformer circuits or both when the welding arc is broken and which is automatically connected again when the welding arc is reestablished.

Another object is to provide means for cutting off comparatively high open circuit voltage at the electrode immediate after the welding arc is broken by the operator and to effect a voltage vdrop to a relatively safe value by a current fur# nished from a former.

A further object of the invention relates'to the provision of a small low rating control transformer to provide current of a safe voltage when the high open-circuit voltage of the welding transformer is cut off wherein the control transpower from the same high voltage line that feeds the'welding transformer.

'I'he foregoing and other objects of the invention are attained by the arrangement illustrated in the accompanying drawings in which;

Fig. 1 is a circuit diagram for an A. C. arc

Welder wherein means are provided for breaking small low rating control transonly the secondary circuit of the welding trans-- former;

Fig.- 2 is a similar diagram wherein means are provided for breaking both the primary and secondary circuits of the-'welding transformer; and

Fig. 3 is a circuit diagram of an automatic safetyy control arrangement for D. C. arc welding showing the motor-generator operated from a 44o-volt 3-phase line.

The arrangement illustrated in Fig. 1 will op# crate to isolate the high open-circuit A. C. volt age of the welding transformer from the electrode holder when the welding arc is broken to cease welding, whereupon a control voltage of 24 the electrode cable while the electrode is not being used, for welding. Upon contact ofthe welding electrode to the work to again commence welding, the

strike an arc and control circuit operates to reconnect the welding transformer secondary to vthe electrode holder and impress full welding voltage of 25 to 40 volts on the welding'lcircuit.

The arrangement shown in Fig. 2 in addition 4to cutting out the secondary also operates to open the primary circuit of the Welding transformer which prevents any power drain Aby the transformer when it is not being used for welding. It will readily be appreciated that considerable saving in power consumption is thus cfmally open contactors fected, especially in large shops Where a great many arc Welders may be connected to the power system.

'Ihe circuit for providing the automatic con- -trol arrangement for the method of arc welding herein disclosed includes the following elements making up the system as a whole:

' A 50 volt ampere step-down transformer I0 provides control energy. 'I'he primary winding II of the control transformer is connected across the 440 volt lines I2 and I3 which may be of 25 or cycles and the secondary I8 delivers current of 24 volts at 25 or 60 cycles.

The vwelding transformer I5 also has its primary connected directly across the 440 volt lines I2 and I3 by means of wires 33-48 and 49. The secondary 38 delivers welding current of 25 to 40 volts.

A 24 volt relay 29 controls operation of nor- 30 and 3l.

A voltage responsive relay 2l of 115 volts is provided with normally closed contactor 26.

Relay 35, energized directly from the 440 volt lines through the contacto?" 3I on the control relay, operates power contactar 25 to break the welding transformer secondary circuit "-42 by means of contact 40. In one phase of the invention a contacter 50 also actuated by this relay operates to break the primary circuit when the welding circuit is opened.

Two interlock contactors, lay 35, are provided, one of them beinga normally closed contact 23 and the other a normally open contact 39. The normally closed interlock functions to isolate the control circuit voltage from the welding circuit voltage when contactor 40 closes and the normally open interlock preoperable by the re-l K@ out of the control relay 29 or its contacts, should the contactor til open under load and draw an arcv at the contacts which might hang on ,sufficiently to feed through the normally closed interlock 23 and damage some part of the control circuit. Normally the contactor @c will not open under load since it is merely an automatic switch operating as an incident to the opening of the welding circuit and is not intended to be used to break the welding current under load but it might open where some mechanical shock disturbs the contacts of relays 21 or t.

In the operation of the system when the elec trode lli touches the work il to strike an arc the following starting circuit is set up to energize the control 29; n

From the secondary i'of the control transformer I9 the current courses through wire i9, including the fuse 20, and wire Zito the work l1. From the work it passes through the electrode I6, wire 22, normally closed contact 23 of the power contactor 25, through wire 24 and the normally closed contact 26 of the relay 21, thence through the coil 28 of the control relay 29 and back to the other side of the control transformer secondary. With this circuit complete the control relay 29 is, of course, energized to close both of the normally open contacts 39 and 3l. When contact 30 closes a holding circuit for the control relay, maintaining the energization of its operating coil 28, is established as follows:

The current travels from the control transfor-mer secondary I8 through wire 32,over the contact 30 and thence to wire 24 through the contact 26 0f relay 21 and through coil 28 of the relay 29 back to the secondary of the transformer I9. The control relay coil 28 thus remains energized to hold both contacts 39 and I-closed until the contact 26 on relay 21 is opened.

An actuating circuit for the power contactor 25 when the control relay closes contact 3l is set up as follows:

Current passes from supplr line i2 through wires 33 and 34 to the coil 36 of power contactor relay 35 and through wire 31 over contact, 3l of the control relay to the other side 3 of the M0 volt supply line. Thus the operating coil of the relay 35 is energized to actuate the power contactor 25 and thereby close the main current carrying contact and open the normally closed interlock contact 23 and close the normally open interlock contact 39. Closing of the main power contactor 4I) sets up the main welding circuit from the secondary 38 of the welding transformer I5 through wire 4I over contact 4E and wires 42 and 22 to the electrode I5. The welding current thus passes through the work I1 and through wire 2l back to the other side of the welding transformer secondary. When the normally closed interlocking contact 23 is opened upon energization of the main power contactor operating coil 36, the voltage of the control transformer I0 is definitely isolated from the heavier voltage of the welding transformer I5, but no change is otherwise had in the operation of :the system.

During this same operation of the main power contactor 25, the system is prepared for subsequentl welding operations by the closing of normally open interlock contactor 39 which establishes a. secondary control or resetting circuit as follows:

Through wires I9 and 43 and over the contactor 39 and the wire 44, current from the welding transformer secondary 38 passes to the coil of voltage responsive relay 21 and then through asegura wires Q5 and S2, over contactor fifi and through wire di to the other side of the welding trans former secondary. This resetting circuit energizes the relay 21. However, the relay 2"? is set to operate only when the voltage has reached a predetermined value and which cannot be reached during the welding operation, since the welding voltage of 25 to 4G volts is not high enough to actuate the relay but only when the electrode E5 is separated from the work. il, thus.

the relay cannot operate to open its contact until the Voltage of the welding transformer secondary has reached the value for which the relay is set. When the electrode is removed from the worlr the welding current is immediately reduced and the voltage of the secondary 38 instantly rises to a value of from 80.to volts. When the voltage reaches the value for which the voltn age responsive relay 21 is set, the relay will operate to open the contact 26 which is disposed in the holding circuit for the control relay 29, and therefore, when contact 26 opens, relay 29 is irnmediately deenergized and opens both of its contacts 36 and 3i. When the contact 3I opens, the operating coil ofthe power contactor 25 is deenergized allowing the contactor to return to-normal position. When the contactor 25 is deenergized, the contact 23 closes to ,prepare the control circuits for subsequent welding operations and contact 39 opens thereby' deenergizing the coil l5 of relay 21 to restore' contact 26 to its normally closed position and thus prepare the holding circuit for the control relay 29 for the next welding operation. As the contactor 25 is restored to normal deenergized position, the main power contact 49 opens to break the welding circuit through the welding transformer I5 and the electrode I6, thus isolating the welding transformer secondary from lthe electrode and restoring the 24 volt control voltage to the electrode.

The primary winding I4 of the welding transformer may also be out out of the circuit simultaneously with the secondary 39 thereby eliminating all high voltage when the welding operation is not being performed. An additional contact 5 0, as shown in Fig. 2, operable with the main power contactor 25, is disposed in the one side 33-48 of the circuit 33--48 and 49 from thc 440 volt circuit I2 and I3 to the welding transformer primary, thereby to open the circuit through the primary at the same time that the circuit through the secondary is opened by means of the contact 40. In this manner all high voltage is automatically eliminated as soon as each welding operation is completed and the circuit is reset for subsequent operations. This arto matic cutting out of the high voltage not only increases the safety of A. C. arc-welding but also eliminates the power consumption of the welding transformer when the welding machine is not actually welding and this power saving will be appreciable in any plant where a large number of arc Welders are connected to the power lines, When welding transformers not under load are leftI on the power line, their power factor is very low since the load is highly inductive and this low power factor load tends to drag down-the system power factor. Removing idle transformers from the line by automatically disconnecting the welding transformer primary, apprecably improves the system power factor. As shown in Figs. 1 and 2, a power factor corrective device may be utilized in the form of a capacitor 41 indicated as being connected across the lines 33 and 49 leading from the supply lines I2 and I3 because it enables arc Welders and such l61 through wire 8|, over 2,364,372 to the primary to improve the power factor,

and disposed as shown, the capacitor would be left on the 440 volt line at all times thereby to;-

obtain the corrective benefit' of the power system improvement whether the welding operation is being performed or not.

A particular feature of the foregoing arrangement lies in the fact that it provides a normally deenergized control circuit which is not disconnected during welding operations and wherein the relays 28 and 21 and the contactor 4 8 have no current flowing through them when the electrode is not welding and the use of the normally closed interlock contactor 23 to isolate the control circuit voltage completely from the welding circuit voltage whereby the control circuit and the welding circuit operate entirely independently of each other is especially advantageous the relays to operate at their intended voltage values without any vibration or chattering of contacts. y

The automatic safety features of this invention may also be utilized in connection with D. C.

an arrangement is illustrated in Fig. 3 wherein a 3phase A. C. motor 60, for driving the welding generator 6l by means of shaft 59, is shown as connected across the 3- phase supply lines 82, 68 and 84. The 50-volt ampere control transformer 65 has its primary 86 also connected across the 440 volt supply lines 62 and 63.

In the operation of the D. C. arrangement when the electrode 68 is engaged with the work 68, a control circuit is established from the 24 volt secondary 61 of the control transformer through wire 10, including a 10 ampere fuse 1l, and wire 12 to the work 68. From the w'ork the current passes through the electrode 68, wire 18, through wire 14, passing over normally closed contacts and'16 and through coil 11 of the control relay 80 to the other side of the control transformer secondary. Completion of this starting circuit energizes the control relay 88 which closes both of the normally open contacts 18 and 19. When the contact 18 is closed, a holding circuit for maintaining the energization of the control relay is set up from the secondary contact 18 and through wire 14, over contact 16 of the relay 82 and through coil 11 of the control relay back to the other side of the secondary thereby to maintain the energization of the relay 88 to hold both of its contacts 18 and 18 closed until the contact 16 on voltage responsive relay 82 is opened.

Closing of the contact 18 by the energization of the control relay 88 completes an actuating I circuit for themain power contactor 85. The current passes from the A. C. supply line 62 through wire 83 to the relay coil 84 ot the main power contactor 85 and then through wire 86 over contact 18 backvto the other side of the A. C. supply line 83. Energization of the main power contactor relay coil 84 by the completion of this circuit actuates the contactor to close its main current carrying contact 80 and opens the interlock contact 15 in the starting .circuit andalso closes the interlock contact 81. When' the main power contact 80 closes the welding circuit is completed from the negative side of the welding generator 6| through wire 88, passing over contact 80 and wire 13 to the electrode 88. 'I'he welding current passes through the work 68 from the electrode and through wire 12 back to the other side or positive terminal of the welding generator. Opening of the interlock contact 15 at the same time that the main power contact is closed does not cause any change in operation but definitely isolates the voltage of the control transformer circuit from the relatively higher voltage of the welding generator. 'I'he interlock contact 81 is closed during the same operation of opening the contact 'l5 and closing the main contact 88 and this prepares the system for subsequent welding operations by setting up a secondary control or resetting circuit with the current travelingfrom the positive terminal of the D. C. welding generator through wires 12, 18 and 8| to the operating coil 88 of voltage responsive relay 82, then through wire 82 overthe interlock contact 81 to wire 1l and thence through wire 88 and over main contact 88 to the negative terminal of the welding generator. This resetting circuit energizes the voltage responsive relay 82 but this relay cannot operate to open its contact 18 until the voltage of the welding generator has risen to the predetermined value for which the relay is set to operate and which does not occur during the welding operation but only when the welding electrode 68 ,is removed fromthe work 69 at which time the welding current is immediately reduced and the voltage of the welding generator instantly rises and when it reaches the value for which the relay 82 is set, the relay operates to open its contact 16. The contact 18 is disposed inthe holding circuit which maintains the energization of the operating coil 11 of the control relay 80 and when the contact i control relay 80 for another welding operation and the main power contactor 80 has opened to break the welding circuit between the D. C. generator and the welding electrode thus isolating the welding generator from the electrode.

From the foregoing it will be seen that an automatic safety control circuit for arc welding has been provided which may be utilized for either A. C. or D. C. Welders whereby a single control arrangement applicable to either may be standardized with only the necessity of ascertaining the particular type of voltage responsive relay to be used in the resetting circuit before application of the arrangement to one or the other system, since the D. C. system uses only this one D. C. relay in the circuit, all of the remaining work circuit, a transformer in said circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer in the circuit having its primary connected to said source ofpower and a secondary delivering control current, a control relay. in circuit with the` control transformer secondary adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay; a contact on the relay adapted to complete said holding circuit upon energization of the relay, a power contactor relay adapted to be connected in circuit with the source of power, a second contact onthe control relay in the actuating circuit for said power contactor relay adapted to initiate energization of the lastnamed relay from lsaid source of power, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contacten the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a voltage responsive relay having a contact disposed in the holding circuit for said control relay, a third contact on the power contactor relay adapted to complete a'resetting circuit from the work circuit transformer secondary to energize said voltage responsive relay and open said contact in the holding circuit, and a fourth contact actuated by the power contactor 'relay adapted to disconnect the work circuit transformer primary from said source of power when the work circuit is unloaded.

2. An automatic safety control circuit including an alternating current source of power, a work circuit, a transformer in said circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer in the circuit having its primary connected to said source of power and a secondary delivery control current, a control relay in circuit with the control transformer secondary adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay, a power contactor relay adapted to be connected in circuit with the source of power, a contact on the control relay in the actuating circuit for said power contactor relay adapted to initiate energization of the last-named relay from said source of power, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contact on the last-named relay adapted to isolate the work circuitfrom said control current when the power i' contactor relay is energized, a voltage responsive relay having a contact disposed in the holding circuit for said controlrelay, a third contact on the power contactor relay adapted to complete a resetting circuit from the work former secondary to energize said voltage responsive relay and open said contact in the holding circuit, and a fourth contact actuated byk the power contactor relay adapted to disconnect the work circuit transformer primary from said source of power when the work circuit is unloaded.

3. An automatic safety control circuit including an alternating current source of power, a work circuit, a transformer in said circuit having' its primary connected to the source of power and having a secondary delivering work current,

a. control .transformer in the circuit having its primary connected to said source of power and a secondary delivering control current, a control relay in circuit with the control transformer secondary adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a power contactor relay adapted to be connected in circuit with the source of power,

circuit transaccepta a contact on the control relay in the actuating circuit for said power contactor relay adapted to initiate energization of the last-named relay from said source of power, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contact on the lastnamed relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, and a contact actuated by the power contactor relay adapted to disconnect the work circuit transformer primary from said source of power when the work circuit is unloaded.

4. An automatic safety control circuit including an alternating current source of power, a work circuit, a transformer in said circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer having a secondary delivering control current, a control relay adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay, a power contactor relay connected in the circuit, a contact on the control relay in the actuatingA circuit for said power contactor relay adapted to initiate energization of the last-named relay, said power contactor relay having a main contact adapted to complete lthe work circuit through said work circuit transformer secondary upon energization of vthe power contactor relay, a second contact on the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a Voltage responsive relay having a contact disposed in the holding circuit for said control relay, a third contact on the'` power contactor relay adapted to complete a resetting circuit to energize said voltage responsive relay and open said vcontact in the holding circuit, and a fourth contact actuated by the power contactor relay adapted to disconnect the work circuit transformer primary from said source of power when the work circuit is unloaded.

5. An automatic safety control circuit including an alternating current source of power, a work circuit, 9, transformer in said circuit having its primary connected to the source 4of power and having a secondary delivering work current, a control transformer in the circuit having its primary connected to said source of power and a secondary delivering control current, a control relay in circuit with the control transformer secondary adapted t0 be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay, a contact on the relay adapted to complete said holding circuit upon energization of the relay, a. power contactor relay adapted to be connected in circuit with the source of power, a second contact on the control relay in the actuating circuit for said power contactor relay adapted to initiate energization of the lastnamed relay from said source of power, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contact'I on the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a voltage responsive vrelay having a contact disposed in the holding circuit for said control relay, and a third contact adapted to be connected circuit.

6. An automatic safety control circuit including analternating current source of power, a work circuit, a transformer in said circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer in the circuit having its primary connected to said source of power and a secondary delivering control current, a control relay in circuitI with the control transformer secondary adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay, a power contactor relay in circuit with the source of power, a contact on the control relay in the actuating circuit forsaid power contactor relay adapted to initiate energization of the last-named relay from said source of power, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary uponenergization of the'power contactor relay, a second contact on the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a voltage responsive relay having a contact disposed in the holding circuit for said control relay, anda third contact on the power contactor relay adapted to complete a resetting circuit from the workv circuit transformer secondary to energize said voltage responsive relay and open said contact in the holding circuit.

7. An automatic safety control circuit including an alternating current .source of power, a. work circuit, a. transformer in said -circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer in the circuit having its primary connected to said source of power and a secondary delivering control current, a control relay in circuit with the control transformer secondary adapted to be energized upon completion of a startingcircuit initiated by loading the work circuit, a power contactor relay adapted tol be connected in circuit with contact on the control relay in the actuating cirthe source of power, a i

cuit forsaid power contactor relay adapted to.

initiate energization of the last-named relay from said source of power, said power contactor relay having -a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, and a second contact on the lastnamed relay adapted to isolate the work circuit from said control current when the power contactor relay is energized.

8. An automatic safety control` circuit including,` an alternating current source of power, a work circuit, a transformer in said circuit having its primaryconnected to the source-of power and having a secondary delivering work current, a control transformer'having a secondary delivering control current, energized upon completion-of a starting circuit initiated by loading the workcircuit, a holding circuit for maintainingv the energization of the relay, a power contactor relay connected in the a control relay adapted to be circuit, a contact on the control relay in the actuating circuit for said power contactorv relay adapted to initiate energization of the last-named relay, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contact on the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a voltage responsive relay having a contact disposed in the holding circuit for said control relay, and a third contact on the power contactor relay adapted to complete a resetting circuit to energize said voltage responsive relay and` open said contact in the holding circuit.

9. An automatic safety control circuit including an alternating current source`of power, a Work circuit, a transformer in said circuit having its primary connected to the source of power and having a secondary delivering work current, a control transformer having a secondary delivering control current, a control relay adapted to be energized upon completion of a starting circuit initiated by loading the work circuit, a holding circuit for maintaining the energization of the relay, a power contactor relay connected in the circuit, a contact on the control relay in the actuating circuit for said power contactor relay adapted to initiate energization of the last-named relay, said power contactor relay having a main contact adapted to complete the work circuit through said work circuit transformer secondary upon energization of the power contactor relay, a second contact on the last-named relay adapted to isolate the work circuit from said control current when the power contactor relay is energized, a voltage responsive relay having a, contact disposed in the holding circuit for said control relay, a third contact on the power contactor relay adapted to complete a resetting circuit to energize said voltage responsive relay and open said contact in the holding circuit, and a capacitor located in the circuit to said work circuit transformer primary.

10. An automatic safety control circuit including an alternating current source of power, supplying a work circuit, a control transformer having its primary connected to said source of power and having a secondary delivering control current, a control relay in circuit with said secondary adapted to be' energized upon completion of a starting circuit initiated by loading said work circuit, a holding circuit for maintaining the energization of said relay,

voltage 'responsive relay having a contact in the holding circuit for the control relay, and a third contact on the power contactor relay adapted to complete a resetting circuit from said source of power to energize said voltage responsive relay and open said contact in the holding circuit.

RALPH S. KENRICK a power contactor relay in vcircuit with said source of power, a contact on 

